1. Field of the Invention
This invention relates to a method and apparatus for donor organ preservation, and more particularly relates to a method and apparatus for in situ hypothermic organ protection during organ retrieval.
The science of organ preservation has been rapidly increasing in importance over recent years because of the increase in organ transplantation as a medical procedure. Basically, in organ preservation, an organ such as a kidney, liver, lung or heart is removed from a donor and maintained in viable condition by artificial means. This is done to maintain the organ until the recipient is selected and prepared to receive it.
At the present time, organs of potential donors have often been unavailable to recipients in desperate need of them because of limitation of current procurement techniques.
More specifically, current procurement technology allows the removal of organs from brain-dead trauma victims, that is, heart-beating donors who are otherwise in good physiological state. A large but yet untapped source of transplantable organs is victims of motor vehicle accidents who succumb to their injuries in the emergency room or in the intensive care unit, in other words, non-heart beating donors. Utilization of organs removed from these donor sources is limited, however. The usual legal requirement for obtaining consent from the families of the potential donor prior to retrieval of such organs and the need to secure an operating room result in a delay of at least 4 hours. This delay may cause injury to the organ targeted for removal due to the effects of warm ischemia. In the case of a kidney, for example, the maximum tolerance of kidney-to-warm ischemia is only about 1/2 hour.
Accordingly, in order to procure organs from non-heart beating cadaver sources, the following conditions should be met 1) rapid exclusion of the organ, such as the kidney, from the vascular tree; 2) rapid flush of the organ's microvasculature, resulting in rapid cooling of the organs, for example, to less than 15.degree. C. in the case of a kidney, and removal of red blood cells from the microcirculation; and 3) maintenance of cold temperature of the organ for a given period of time, for example, for 4-5 hours in the case of a kidney.
All of these procedures must be performed with minimal violation of the body, that is, with no major abdominal or chest incision, prior to obtaining familial consent
2. Description of the Prior Art
There exist a number of patents and publications which disclose a method or apparatus for organ preservation. For example, U.S. Pat. No. 4,666,425 (Fleming) discloses a device for perfusing an animal head. The purpose of the perfusing device disclosed in the Fleming patent is stated as being to keep a discorped head (i.e., severed from its body) alive or viable for ultimate transplantation.
FIG. 2 of the Fleming patent illustrates a severed head connected to process equipment and to a brain-dead body through the use of cannulae. The patent states that the main arteries and veins of the head are coupled to the arteries and veins of the neck of the body to complete the circuit. It is stated that the brain-dead body may be kept alive by artificial means so that the organs of the body, such as the kidneys, etc , perform their natural function in treating and oxygenating the blood passing through the discorped head.
Alternatively, and as illustrated by FIG. 3 of the Fleming patent, it is described in the patent that the discorped head may be kept alive by a pumping and treatment circuit, whose terminal ends are connected to the main arteries and veins of the head. It is further stated that the treatment circuit may include pumps 52 and 54 to drive blood in the circuit through the head, and a treatment chamber 56 which may, for example, introduce heparin to the blood to prevent clotting or which may heat or cool the blood in order to raise or lower the solubility of desired or undesired components. The patent describes the circuit as also including an oxygenation chamber 58 to add oxygen to the blood, and a waste removal chamber 60 to remove waste products.
It should be noted, however, that the method disclosed in the Fleming patent relates to keeping an organ (the head) alive, which organ is separated from the body. Accordingly, such a method would be inappropriate where unnecessary mutilation of the body prior to obtaining the consent of the potential donor's next of kin is to be avoided. Such disclosed method is also not performed in situ.
Other patents and publications disclose methods and devices for organ preservation. For example, U.S. Pat. No. 3,995,444 (Clark, et al.) discloses an organ perfusion system, in which it is described that an organ 21 removed from the body is placed into a chamber and connected to a conduit which provides a cold perfusion solution to the organ. The Clark, et al. patent states that the solution draining from the organ collects in a well and is removed through another conduit which passes through an ice bath to effect rapid cooling of the solution, and that the conduits are connected to an oxygenator 12, a pulsating pump 11 and a bubble trap 30, and returned to the organ to effect further cooling of the organ.
It should be noted that the organ has already been removed from the body in accordance with the method disclosed in the Clark, et al. patent, and thus the Clark, et al. patent does not address the problem associated with maintaining the viability of the organs in situ without a major invasion of the body prior to obtaining consent for the removal of the targeted organ.
Also, U.S. Pat. No. 3,660,241 (Michielson) discloses a container for transporting a transplant organ, where the container has a number of apertures through which pass conduits connected to the organ for providing a perfusion solution to the organ. The Michielson patent further states that the container may be filled with a solution to bathe the outside of the organ. Of course, the method and apparatus disclosed in the Michielson patent is for maintaining the viability of the organ after it is removed from the donor and not before.
An article, A Small Perfusion Apparatus for the Study of Surviving Isolated Organs, by Long & Lyons, shows, in FIG. 2B of the article, a diagrammatic representation of a perfusion circuit in which an organ, removed from the donor, is placed in a chamber and connected to a circuit to allow a perfusion solution to pass through it. The article does not disclose a method or apparatus which allows the targeted organ to be cooled in situ.
Also of interest is U.S. Pat. No. 4,192,302 (Boddie). The Boddie patent discloses a perfusion circuit which, through a plurality of shunts, allows blood circulation from the lower part of a patient's body and from the intestines to flow to the heart, while allegedly isolating hepatic venous blood containing toxic agents from the body's general circulation and returning it to a heart-lung machine. It is stated that circuit may be used to perfuse the liver of a patient which has become involved with cancer with extremely high doses of chemotherapy agents while at the same time avoiding the toxic effects of these agents on the patient's body as a whole
The perfusion circuit disclosed in the Boddie patent is shown in FIG. 3 of the patent. The circuit requires a number of catheters for redirecting the patient's blood, and a number of ligatures (such as T1-T6) to hold the catheters in place and to occlude blood flowing into the liver from the hepatic artery.
It is to be noted that the Boddie patent does not disclose a minor invasion of the patient's body, as the perfusion circuit disclosed in the Boddie patent appears to require major surgery, nor does it describe a system or method for preserving organs of a potential donor for transplantation.